I'm trying to developp my first smart contract to make some arbitrage between DEX.
I started by using the code from :
https://github.com/pugzly/token_swap/blob/main/token_swap.sol
But when I execute the swap function with :
_tokenIn : WBNB address
_tokenOut : BUSD address
_amountIn: 0x038d7ea4c68000 //0.001 WBNB
_amountOutMin : from getAmountMin function
_to : My address
I have an error with gas estimation but impossible for me to understand why :
Here is my code :
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.11;
interface IERC20 {
function totalSupply() external view returns (uint);
function balanceOf(address account) external view returns (uint);
function transfer(address recipient, uint amount) external returns (bool);
function allowance(address owner, address spender) external view returns (uint);
function approve(address spender, uint amount) external returns (bool);
function transferFrom(
address sender,
address recipient,
uint amount
) external returns (bool);
event Transfer(address indexed from, address indexed to, uint value);
event Approval(address indexed owner, address indexed spender, uint value);
}
interface IUniswapV2Router {
function getAmountsOut(uint256 amountIn, address[] memory path)
external
view
returns (uint256[] memory amounts);
function swapExactTokensForTokens(
uint256 amountIn,
uint256 amountOutMin,
address[] calldata path,
address to,
uint256 deadline
) external returns (uint256[] memory amounts);
}
interface IUniswapV2Pair {
function token0() external view returns (address);
function token1() external view returns (address);
function swap(
uint256 amount0Out,
uint256 amount1Out,
address to,
bytes calldata data
) external;
}
contract ArbitrageV1{
event approve(uint256 buy1,uint256 _montant);
event estimate(uint256 montan);
address private constant routerPCS = 0x10ED43C718714eb63d5aA57B78B54704E256024E;
address private constant wbnb1=0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c;
function swap(address _tokenIn, address _tokenOut, uint256 _amountIn, uint256 _amountOutMin, address _to) external {
IERC20(_tokenIn).transferFrom(msg.sender, address(this), _amountIn);
IERC20(_tokenIn).approve(routerPCS, _amountIn);
address[] memory path;
if (_tokenIn == wbnb1 || _tokenOut == wbnb1) {
path = new address[](2);
path[0] = _tokenIn;
path[1] = _tokenOut;
} else {
path = new address[](3);
path[0] = _tokenIn;
path[1] = wbnb1;
path[2] = _tokenOut;
}
IUniswapV2Router(routerPCS).swapExactTokensForTokens(_amountIn, _amountOutMin, path, _to, block.timestamp);
}receive() payable external {}
function getAmountOutMin(address _tokenIn, address _tokenOut, uint256 _amountIn) external view returns (uint256) {
address[] memory path;
if (_tokenIn == wbnb1 || _tokenOut == wbnb1) {
path = new address[](2);
path[0] = _tokenIn;
path[1] = _tokenOut;
} else {
path = new address[](3);
path[0] = _tokenIn;
path[1] = wbnb1;
path[2] = _tokenOut;
}
uint256[] memory amountOutMins = IUniswapV2Router(routerPCS).getAmountsOut(_amountIn, path);
return amountOutMins[path.length -1];
}
}
I would be very greatful if you can help me,
UPDATE :
Thanks for your answer Rihe, I just changed my gas settings but it still doesn't work.
UPDATE 2 :
Thanks again, I just removed the transferFrom line as you recommended me.
I still have the Gas Estimation failed error, but it's more detailed :
I know that this error is generally linked to approve problem. Do you have any idea to solve it ?
Best Answer
I believe your gas settings are incorrect. In the Remix IDE you can fix it easily. Please find the below image. I think something like 300000 for gaslimit and 5 gwei for value should be fine.
UPDATE
After checking your code I observed that your swap function may be incorrect. When you call the
swapExactTokensForTokens
, you don't have to manually make a transfer. The router will handle it. You just need to approve it.